fix: avoid repeated daily starlanguage refresh

frontend/src/app/page.tsx

@@ -102,6 +102,7 @@ import {
   requestOnboardingWithRecovery,
 } from "@/lib/onboarding-client";
 import { protectOnboardingPhrases } from "@/lib/onboarding-copy";
+import { preserveShallowEqual } from "@/lib/preserve-shallow-equal";
 import {
   SessionModelPersistenceQueue,
   persistSessionModelSelection,
@@ -1797,7 +1798,7 @@ export default function Home() {
       const latest = await fetchAccount();
       if (!accountRefreshGuard.current.isCurrent(requestIdentity)) return;
       const nextProfile = readProfile(latest.profile);
-      setProfile(nextProfile);
+      setProfile((current) => preserveShallowEqual(current, nextProfile));
       setAccount(latest);
       setAccountError("");
     } catch (caught) {

frontend/src/lib/preserve-shallow-equal.ts

@@ -0,0 +1,18 @@
+export function preserveShallowEqual<T extends object>(current: T, next: T): T {
+  if (Object.is(current, next)) return current;
+
+  const currentRecord = current as Record<string, unknown>;
+  const nextRecord = next as Record<string, unknown>;
+  const currentKeys = Object.keys(currentRecord);
+  const nextKeys = Object.keys(nextRecord);
+
+  if (currentKeys.length !== nextKeys.length) return next;
+
+  for (const key of currentKeys) {
+    if (!Object.hasOwn(nextRecord, key) || !Object.is(currentRecord[key], nextRecord[key])) {
+      return next;
+    }
+  }
+
+  return current;
+}